Grouped letters

Question

Each of the following sets has something in common; that is, the members of each set are related to one another in the same way.

• D, E, and G
• K and Y
• I and O
• N and P
• U, V, and W
• A and R

What trait do they share, and what letter goes with J?

Answer 1

Looking at this

up-to-date list of 118 chemical element symbols ordered alphabetically

We see D, E, and G have

Three symbols (all two-letters) starting with these letters
Db Dubnium, Ds Darmstadtium, Dy Dysprosium
Er Erbium, Es Einsteinium, Eu Europium
Ga Gallium, Gd Gadolinium, Ge Germanium

and similarly, K and Y

Two symbols (one each of one-letter and two-letters)
K Potassium, Kr Krypton
Y Yttrium, Yb Ytterbium

I and O

Three symbols (one one-letter and two two-letters)
I Iodine, In Indium, Ir Iridium
O Oxygen, Og Oganesson , Os Osmium

N and P

Nine symbols (one one-letter and eight two-letters)
N Nitrogen, Na Sodium, Nb Niobium, Nd Neodymium, Ne Neon, Nh Nihonium, Ni Nickel, No Nobelium, Np Neptunium
P Phosphorus, Pa Protactinium, Pb Lead, Pd Palladium, Pm Promethium, Po Polonium, Pr Praseodymium, Pt Platinum, Pu Plutonium

U, V, and W

One symbol (all one-letter)
U Uranium
V Vanadium
W Tungsten

A and R

Eight symbols (all two-letters)
Ac Actinium, Ag Silver, Al Aluminum, Am Americium, Ar Argon, As Arsenic, At Astatine, Au Gold
Ra Radium, Rb Rubidium, Re Rhenium, Rf Rutherfordium, Rg Roentgenium, Rh Rhodium, Rn Radon, Ru Ruthenium

What letter goes with J?

Q as there is no chemical symbol starting with this letter (J and Q are not even in the name of any chemical element or symbol)